High Altitude
- Warm up engine and check ignition timing at idle. Disconnect vacuum hose from the distributor sub-diaphragm and plug hose end.
- Timing must remain stationary for more than 1 minute. If timing changes, replace check valve. Stop engine and reconnect hose to check valve.
- Disconnect 2 hoses on top of HAC valve. Blow air into each hose and check that air flows into carburetor. Reconnect hoses to proper locations.